492 
HARKER : LAKE DISTRICT IGNEOUS ROCKS. 
(c) Mica-Lamprophyres. — These dyke-rocks, sometimes termed 
" mica-traps,"' are too well known to need description, their 
richness in biotite being a very striking feature. It may be 
mentioned that, while the typical lamprophyres are strongly 
contrasted with the often associated acid dykes just mentioned, 
we find in certain places varieties intermediate between the 
two (e.g., Stakeley Folds, near Shap Wells, and Long Sled- 
dale.) 
The remaining intrusions probably belong to a still later period. 
There is no direct evidence of their age, except the fact that 
they are younger than the great crust-movements ; but their 
very close petrographical resemblance to Tertiary Rocks in 
other parts of Britian raises a certain presumption that they 
belong to the same period, 
(r/) The Carrock Fell intrusions. — The principal rocks here are two, 
gabbro and granophyre. The gabbro is a highly variable 
rock. Usually it is of medium or moderately coarse grain, 
only exceptionally very coarse, with large lustrous crystals 
of augite. The central part of the mass is a quartz-gabbro, 
the quartz sometimes visible in interstitial grains, but com- 
monly in micropegmatite detected only in thin slices. The 
augite has a strong striation parallel to the basal plane. This 
relatively acid rock passes gradually through normal gabbro 
(i.e., without quartz), into an extremely basic rock at the edge 
of the mass. Here felspar is reduced to a minimum, and 
about one-fourth of the rock is made up of titaniferous iron- 
ore. The granophyre has the dull confused aspect character- 
istic of a micropegmatitic rock, and contains scattered crystals 
of oligoclase and abundant little dark specks, which are 
augite-crystals. 
(e) Dolerite and Andesite Dykes. — A few dykes have been observed, 
and possibly more remain to be detected, which resemble 
known Tertiary dykes, and are perhaps to be referred to 
that period. They are apparently less basic on the whole 
than the older dolerites, and they are in a fresher 
condition. 
